Activity of optically active 1-benzyltetrahydroisoquinoilnes in dopaminergic and adrenergic assays is restricted to the S-isomer. Both racemic isoquinolines, 1-(o-hydroxybenzyl)-6-hydroxytetrahydroisoquinoline and racemic 1-(m-hydroxy-benzyl)-6-hydroxytetrahydroisoquinoline showed good inhibitory activity in the Alpha-adrenergic receptor assay and in the Beta-adrenergic receptor assay respectively.